instr: Kevin Bonine t.a.: Kristen Potter

Transcription

1 Lecture 17, 18 Oct 2005 Chapter Circulation, Oxygen and Carbon Dioxide Transport Vertebrate Physiology ECOL 437 (aka MCB 437, VetSci 437) University of Arizona Fall 2005 instr: Kevin Bonine t.a.: Kristen Potter 1 1. Circulation 2. Heart Muscle 3. Heart Function 4. Diving Response Reading of Text: Randall et al. Start with Chapters 23 & 24 (skip the invert material if you like) Next week we will discuss 21 & 22 (read Chapter 20 quickly) EXAM THURSDAY, Paper Drafts today 2 1

2 AZDStar 18 Oct Short Quiz ECOL Oct 2005 mean median max 1. Draw a graph that represents the length-tension curve. 3 points Explain, mechanistically, why the curve above has the shape it does. 2 points 3. Describe two characteristics that differ between muscle fiber types. 2 points 4. Explain what ryanodine and dihydropyridine receptors are and what they do. 3 points min s.d. Include Name and Lab time 4 2

3 From body From Lungs Chordae tendinae To Lungs (Eckert, 12-4) Mammalian Heart To Body via AORTA 5 Cardiac Muscle (the other striated muscle) -Small muscle fiber cells with only one nucleus -Individual fibers are connected to neighbors electronically via gap junctions -Two types of fibers: 1. Contractile (similar to skeletal muscle) 2. Conducting (including pacemaker cells) Do not contract, but transmit electrical signal -Cardiac contraction myogenic (arises within heart) Can be influenced by autonomic nervous system (alpha, beta adrenoreceptors increase [Ca2+]) -Long-lasting AP with long plateau phase, and long refractory period - why? 6 3

4 Cardiac Muscle (the other striated muscle) -Intracellular calcium from SR and across plasma membrane (unlike in skeletal) -Dihydropyridine receptors in T-tubules are voltage-activated calcium channels -Ryanodine receptors then release more calcium from SR into the cytoplasm (calcium-induced calcium release) -During relaxation, Calcium pumped actively back into SR and out across plasma membrane 7 Vertebrate Circulation (too big for diffusion!) Heart is main propulsive organ Arterial system -distributes blood -regulates pressure Capillaries -transfer between blood and tissues Venous system -return blood to heart -storage reservoir Divided into Central and Peripheral Focus on Mammalian Circulation with some exceptions 8 4

5 Gravity and BP 9 Knut Schmidt_Nielsen 1997 Circulatory Roles and Components Valves control direction of blood flow Sherwood 1997 Smooth muscle controls diameter of peripheral vessels, thereby altering resistance and flow to different tissues 10 5

6 Circulatory Roles and Components -Gases (CO 2, O 2 ) -Nutrients -Waste -Hormones -Antibodies -Salts -etc. -Temperature Regulation RBCs -Blood volume 5-10% of body volume Vander Development of Terrestrial Circulatory System: gills simple (and linear): 1. Blood goes to gills 2. O2-rich blood goes to tissues 3. O2-poor blood goes to heart 4. Blood gets pumped back to gills lungs more complex because get 2 circuits in parallel: 1. Pulmonary circuit (lower pressure) 2. Systemic circuit (higher pressure) 12 6

7 Spongy vs. Compact Myocardium Hill et al. 2004, Fig (Eckert, 12-16) Fish Circulation through gills 14 7

8 Addition of lungs more complicated (Eckert, 12-16) Water vs. air 15 Mammalian Circulation Two parallel closed circuits: 1. Pulmonary (lower press.) 2. Systemic (Eckert, 12-3) Note venous reservoir 16 8

9 Tissue Beds in Parallel, not Series 9-3, Sherwood 1997 All cells within 2-3 cells of a capillary Can control amount of flow to each tissue independently 17 In addition to Heart, Blood also moved via 1. Elastic recoil of arteries 2. Squeezing of vessels during body movement 3. Peristaltic contractions of smooth muscle in vessels 18 9

10 From body From Lungs Chordae tendinae To Lungs (Eckert, 12-4) Mammalian Heart To Body via AORTA , Vander 2001 No valves as Enter Atria Mammalian Heart 20 10

11 Non-Mammalian Heart Examples: Amphibians and Reptiles (except crocodilians) with 3 chambers (= one ventricle, two atria) -incompleteventricular septum -BUT separate rich and poor blood -AND alter pressure in systemic and pulmonary -able to alter flow to systemic or pulmonary circuit 21 Amphibians: Cardiovascular System only vertebrates where O 2 poor blood to skin (as well as to lungs) adults with paired pulmocutaneous arteries divide into two branches 1. Pulmonary 2. Cutaneous (to flanks and dorsum) skin provides 20-90% O 2 uptake % CO 2 release 22 11

12 Cardiovascular System Gets rich FROG Heart Gets poor conus arteriosus w/ spiral valve trabeculae (create channels) role of Tb and HR Pough et al., 2001 Fig Cardiovascular System Reptilian Heart (not crocs) RAA = right aortic arch LAA = left aortic arch PA = pulmonary artery (no conus arteriosus, no spiral valve) 2 systemic arches and one pulmonary artery from single ventricle BUT, single ventricle functions as THREE 3-chambered heart anatomically 5-chambered heart functionally Muscular Ridge Pough et al., 2001 Fig 6-9a RA = right atrium LA = left atrium 24 12

13 Reptilian Heart (not crocs) not primitive RAA = right aortic arch LAA = left aortic arch PA = pulmonary artery 3-chambered heart anatomically 5-chambered heart functionally IVC = intraventricular canal AVV = atrioventricular valve Muscular Ridge Muscular Ridge CP = cavum pulmonale CV = cavum venosum CA = cavum arteriosum Pough et al., 2001 Fig Reptilian and Amphibian Circulation Cardiac Shunts (in 3-chambered heart) 1. temperature regulation 2. breath holding (diving, turtle in shell, inflated lizards) 3. stabilize O 2 content of blood when breathe intermittently R to L O 2 poor to systemic via aortic arches (short delay between valves opening) L to R O 2 rich to pulmonary artery (longer delay between valves opening) 26 13

14 Mammalian fetus: Ductus arteriosus (R -> L shunt, lung bypass) -pulmonary artery to systemic arch -when lung inflate resistance down (pulm) -when lose placental circ. resistance up (syst) -closes at birth Foramen ovale (interatrial shunt R -> L) -hole in wall between atria -closes at birth 27 Bird chick: Chorioallantois = network of vessels under shell surface Interatrial septum -R -> L shunt, lung bypass -closes after hatching 28 14

15 Electrical Activity in the Mammalian Heart RA LA RV LV Influenced by autonomic NS Vander Cardiac Cells electronically linked by Gap Junctions Sherwood 1997 (except from atrial to ventricular cells ) 30 15

16 Electrical Activity in the Mammalian Heart Vander Recall AP and refractory period differences (Eckert, 12-7) 32 16

17 Types of Cardiac Cells: A. Contractile B. Conducting ~ autorhythmic SA node AV node ~ fast-conducting Internodal Interatrial Bundle of His Purkinje Etc. Vander Sherwood

18 Types of Cardiac Cells: A. Contractile B. Conducting - 1 autorhythmic SA node AV node -1 fast-conducting Internodal Interatrial Bundle of His Purkinje Etc. Pacemakers: -Normally HR driven by SA node -Others are Latent pacemakers -Called Ectopic pacemaker when node other than SA driving HR 35 Sherwood 1997 ~ SA node ~ latent rate Sherwood

19 SA AV The Heart Rate Train other oops Sherwood , Sherwood 1997 Which way would you alter channel permeabilities to speed or slow HR?? ~Transient Ca 2+ channels K +, Na + Autorhythmic Cardiac Muscle (e.g. SA node) 38 19

20 Sherwood 1997 Contractile Cardiac Muscle Ca 2+ current maintains plateau Vander (Eckert, 12-8) (Q,R,S masks atrial repolarization) 40 20

21 (Eckert, 12-8) 41 Wiggers Diagram Valves open/close where pressure curves cross 760 mmhg = 1 atm = 9.8 m blood 1: , Vander

22 Sherwood 1997 Atrial Kick Heart filled ~same with increased HR 43 Sherwood 1997 Frank-Starling Curve Systole = Ventricular Emptying Diastole = Ventricular Filling (rest) Vander

23 Heart Work Loops (Eckert, 12-13) 45 Cardiac Output: CO = cardiac output (ml/min from 1 ventricle) SV = stroke volume (ml/beat from 1 ventricle) = EDV ESV (end-diastolic end-systolic volume) HR = heart rate (beats/min) CO = HR x SV MABP = CO x TPR MABP = DP + 1/3(SP-DP) - Heart can utilize different types of energy sources (unlike brain) 46 23

24 HR control Parasympathetic vs. Sympathetic (Eckert, 12-5) 47 Gravity and BP 48 Knut Schmidt_Nielsen

25 Cardiac Output 6x Exercise Oxygen Consumption X 20 Knut Schmidt_Nielsen Peripheral Circulation - Endothelium lining vessels - Middle layer with smooth muscle (esp. arteries) - Outer fibrous layer Capillaries with ~ only Endothelium 50 25

26 (Eckert, 12-26) 51 Peripheral Circulation Compliance vs. Elasticity ~ Veins vs. Arteries Volume Reservoir vs. Pressure Reservoir 52 26

27 Volume Reservoir vs. Pressure Reservoir 14-34, Vander 2001 (Eckert, 12-27) ~Constant P and Q at Capillaries! 53 Venous System - low pressure (11 mm Hg or less) - thin walled veins with less muscle -more compliant and less elastic - valves - blood moved by skeletal muscle (and smooth) - breathing creates vacuum (low pressure) in chest to aid blood flow to heart 54 27